As high-tech licenses become increasingly hard to forge, the Department of Motor Vehicles has found that one popular approach to obtaining fraudulent license is for someone to pose as a friend or colleague in an effort to get an official license. New high-tech software uses facial recognition to warn officials if the face of the person being licensed matches someone already licensed.

However, there's one problem -- the algorithms often fail if people are making different faces in the two photos. So four states -- Arkansas, Indiana, Nevada and Virginia -- are telling drivers to wipe that grin off their face. No more happy days for licensing, the states have declared, drivers must adopt "neutral facial expressions".

Carnegie Mellon University robotics professor Takeo Kanade acknowledges that the move is necessary given the poor state of facial recognition technology when it comes to facial expressions. Researchers still have yet to catch up to the inherent processing capability of the human brain, which can recognize familiar faces in a broad variety of expressions.

Karen Chappell, deputy commissioner of the Virginia DMV says that the smile ban is necessary to "make the comparison process more accurate."

Some citizens who were initially offended are changing their tune, deciding that the rule is in the best interest of national security. States Elaine Mullen of Great Falls, Va., "It's probably safer from a national-security point of view."

Arkansas, Indiana and Nevada do still allow small smiles. Currently 31 states in total do computerized matching of driver's license photos, and 3 others are considering it. Of the 27 other states without anti-smiling policies, many are considering adopting similar measures. Some states though are resisting the movement. Pennsylvania Transportation Department spokesman Craig Yetter, states, "People can smile here in Pennsylvania."

Even without a smile-ban, Illinois stopped 6,000 people from getting fraudulent licenses since 1999, according to Beth Langen, the state head of Drivers Services.